The Boas, properly so called, have the scales smooth; labial shields smooth, not pitted; the body compressed, tapering to the tail, which is long and prehensile; the head is comparatively small, being enlarged behind, and contracted towards the muzzle, which is rather short. The crown is covered with scales; the nostrils lateral, between two plates. Four species of this genus are recognised by naturalists, all of which have been described by travellers as the true Boiguacu, or _Boa-constrictor_ of Linnæus. This species has the scaly circle of the orbit separated from the upper labial plates by one or two series of scales. A large chain consisting of blackish hexagonal spots, alternating pale oval stains, notched and jagged, extending the whole length of the back, and forming a very elegant design. This species seems to be strictly confined to tropical America. Humboldt found it in Guiana, and the Prince de Wied observed it in Brazil. All the specimens in the British Museum are from that part of the New World. This is supposed to be the Tlicoatl and Temacuilcahuilia (the words meaning "fighting with five men"), described by Hernandez, the latter name being derived from its size and strength. "It attacks," he says, "those it meets, and overpowers them with such force, that if it once coils itself round their necks, it strangles and kills them, unless it bursts itself by the violence of its own efforts." The same author states that he has seen Serpents as thick as a man's thigh, which had been taken when young by Indians and tamed. That this Boa attains an immense size is a well-established fact. Shaw mentions a skin in the British Museum, in one of his lectures, which measured thirty-five feet in length. Three other species--the Lamanda (_B. diviniloqua_), from Santa Lucia; the Emperor (_B. imperator_), a native of Mexico; and _B. eques_, the Chevalier Boa of Peru--are all to be occasionally seen in the Zoological Gardens. The _Boa anaconda_, more properly _Eunectes murinus_, is also a native of tropical America. The name of Anaconda has become well known through Mr. Lewis's celebrated tale, so called, in which its predatory habits are displayed in such a manner as to enthral and fascinate the reader, as the author makes the reptile fascinate its victim. The name, Mr. Bennett tells us, is of Cinghalese origin, and is popularly applied to all very large Serpents. This species is of a brownish tint, with a double series of colours extending from head to tail; the sides are covered with annular spots with white disks surrounded by blackish rings. Seba has represented this creature lying in wait for Mice; but this is probably the prey of the young Anaconda. Another provincial name, "El Troga Venado" (the Deer Swallower), is probably applied to the matured Reptile. [Illustration: Fig. 16.--Anaconda (_Eunectes murinus_).]